This study was carried out with the aim to identify the characteristics and determine the direct or indirect effect of soil and water quality on the agar content of seaweed Gracilaria verrucosa in acid sulfate soil (ASS)-affected brackishwater ponds in South Sulawesi Province, Indonesia. The study was conducted in ponds of North Luwu and Sinjai Regencies. The soil quality is defined as the independent or exogenous variable; the water quality as an intermediate, dependent, or endogenous variable; as well as the agar content of seaweed as a dependent or endogenous variable. The influence of environmental factors was identified through path analysis applications. In general, the water quality can support the culture of seaweed in ponds. The results of the research showed that of the 17 soil quality variables analyzed, 2 variables were found, namely Fe content and pH_KCl which influenced the agar content of seaweed. Another result was that of the 9 water quality variables, and 2 variables were also found, namely salinity and NO₃^- content which influenced the agar content of seaweed. Soil Fe can reduce the agar content while soil pH_KCl, salinity, and water NO₃^- content can increase the agar content of seaweed in ASS ponds in South Sulawesi.